The present invention relates to a television receiving apparatus capable of receiving a television broadcasting signal in correspondence to two different kinds of channel plans, and more particularly to a television receiving apparatus having an automatic discrimination auto-search function for two kinds of channel plans.
Conventionally, a television receiving apparatus has been provided which is capable of receiving selectively either the TV (television wave) broadcasting or the CATV (cable television) broadcasting. This television receiving apparatus may have an automatic discrimination auto-search function for automatically discriminating whether the receivable channel plan is for TV broadcasting or for CATV broadcasting (e.g., see JP-A-11-4388).
As disclosed in this publication, noticing that the CATV broadcasting has the channels assigned in a specific frequency band (e.g., 300 MHz to 400 MHz) in which none of the TV broadcasting channels are assigned, a CATV mode is discriminated if any broadcasting station exists in the specific frequency band, or a TV mode is discriminated if no broadcasting station exists in the specific frequency band. And in accordance with a result of discrimination, the channel preset is executed, and the channel tuning control is performed, based on the content of the channel preset.
In this way, the conventional television receiving apparatus discriminates a CATV mode or a TV mode in such a manner that the CATV mode is discriminated if a station exists in a specific frequency band in which the TV broadcasting channel is not assigned.
However, with such a conventional discrimination method, since a station may be discriminated to be present due to the influence of the noise, in spite of the station being absent, there is the possibility that a false discrimination may occur by falsely discriminating the CATV mode in spite of the TV mode in essence. Therefore, to reduce such false discrimination as least as possible, the CATV mode may be discriminated in the case where two or more stations exist in a specific frequency band, but in anyway, it is impossible to eliminate the influence of the noise completely.